Huawei H12-831_V1.0 Exam With Confidence Using Practice Dumps

Comprehensive and Detailed In-Depth Explanation:

1. Understanding the Routing Issue

R1 and R4 are BGP routers and have an IBGP connection.

R2 and R3 are OSPF-only routers (they do not run BGP).

Networks 10.1.1.0/24 and 10.4.4.0/24 are advertised into BGP but not OSPF.

PC1 (10.1.1.1) and PC2 (10.4.4.1) need communication, but their networks are not known to OSPF routers R2 and R3.

To fix this, we need a method that ensures R2 and R3 learn the routes for 10.1.1.0/24 and 10.4.4.0/24.

2. Evaluating Each Answer Option

Option A: " Deploy policy-based routing on R1 and specify R2 as the next hop for traffic from PC1 to PC2. "

Incorrect.

Policy-Based Routing (PBR) does not solve the issue of missing routes in OSPF.

Even if R1 forwards traffic to R2, R2 does not know how to reach 10.4.4.0/24, causing packet drops.

A proper routing protocol solution is required instead of PBR.

Option B: " Deploy MPLS and LDP on R1 to R4 and establish LSPs for routes 1.1.1.1/32 and 4.4.4.4/32. "

Incorrect.

MPLS requires label-switched paths (LSPs) but does not distribute routing information itself.

The real problem is that R2 and R3 do not have routing entries for 10.1.1.0/24 and 10.4.4.0/24.

MPLS does not fix the missing route advertisement issue.

Option C: " Run BGP on R2 and R3, and establish full-mesh IBGP connections in AS 123. "

Correct.

If R2 and R3 run BGP, they can form IBGP sessions with R1 and R4 and learn routes 10.1.1.0/24 and 10.4.4.0/24 via BGP.

R2 and R3 would then be able to forward traffic correctly between PC1 and PC2.

This is a valid method to fix the issue.

Option D: " On R1 and R4, import routes 10.1.1.0/24 and 10.4.4.0/24 into OSPF. "

Correct.

By redistributing BGP routes into OSPF, R1 and R4 can ensure that R2 and R3 learn the missing networks (10.1.1.0/24 and 10.4.4.0/24) via OSPF.

This allows full reachability without running BGP on R2 and R3.

This is another valid method to fix the issue.

Final Answer:

✅ C and D are correct.

HCIP-Datacom-Advanced Routing & Switching Technology References:

BGP and OSPF Route Redistribution

IBGP Full-Mesh Requirement and Route Propagation

How Policy-Based Routing Works and Its Limitations

All four methods can provide the required return path. R2 and R3 import the IS-IS route 2000::6/128 into OSPFv3, allowing R4’s Echo Request to reach R6. The remaining requirement is a route on Level-1 router R6 for returning the Echo Reply toward R4, because the OSPFv3 routes are not imported back into IS-IS.

The command:

ipv6 default-route-advertise always level-1

unconditionally originates an IPv6 default route in a Level-1 LSP. Configuring it on either R2 or R3 enables R6 to install ::/0 through that router.

The alternative command:

attached-bit advertise always

forces a Level-1-2 router to set the ATT bit in its Level-1 LSP. When Level-1 router R6 receives an LSP with ATT set, it creates a default route toward the advertising Level-1-2 router. Both R2 and R3 are Level-1-2 routers and participate in the OSPFv3 domain, so either can forward R6’s return traffic toward R4.

Thus, either default-route mechanism can be configured on either R2 or R3, making all four options valid. Huawei IS-IS command reference

???? Key Concept:

IS-IS is a Layer 2 routing protocol and does not rely on IP addressing to establish neighbor relationships. Unlike OSPF, IS-IS runs directly over the data link layer (CLNS - ISO 8473) and uses MAC-level communication for neighbor discovery.

???? IPv6 Addresses in the Scenario:

R1 Interface:

2000:12::1/64

2000:21::1/64

R2 Interface:

2000:12::2/127

2000:21::2/127

Even if IP prefixes on the interfaces are mismatched, IS-IS adjacency can still be formed, because:

IS-IS does not use IP address matching for adjacency formation.

What matters is that the interfaces are on the same Layer 2 segment and IS-IS is enabled on both sides.

✅ Final Answer: B. FALSE

Official Huawei Extract:

" IS-IS operates at Layer 2 and establishes neighbor relationships regardless of IP address configuration. As long as IS-IS is enabled and interfaces are connected at Layer 2, a neighbor relationship can be established—even with different IP prefixes. "

— [Huawei HCIA-Datacom Certification Guide – IS-IS over IPv6 Chapter]